1. Field of the Invention
The present invention relates to a label printer that prints on linerless label paper wound in a roll.
2. Description of Related Art
Label printers for printing labels using linerless label paper have been developed as a way to eliminate the waste created by the liner when printing on label paper with a web liner.
An example of a label printer that can print on such linerless label paper is described next with reference to FIG. 3 and FIG. 4.
The label printer 1 has a roll paper compartment 7, a label transportation path 13, a print head 15, a cover 19, and a case 17. The roll paper compartment 7 holds a label paper roll 5 of linerless label paper 3 wound in a roll. The label transportation path 13 carries the linerless label paper 3 pulled off the label paper roll 5 from a label paper entrance 11 facing the inside of the roll paper compartment 7 to the label paper exit 12. The print head 15 prints on the linerless label paper 3 as it travels through the label transportation path 13. The cover 19 is attached to the case 17 so that it can open and close the roll paper compartment 7 and the label transportation path 13.
The print head 15 is a thermal print head that prints using a thermosensitive printing method.
The linerless label paper 3 has a printing surface that is coated with a thermosensitive layer, and an adhesive coating on the opposite side. The linerless label paper 3 is wound into the label paper roll 5 so that the adhesive side of the linerless label paper 3 is on the inside.
A platen roller 16 that presses the linerless label paper 3 to the print head 15 is disposed at a position opposite the print head 15 with the linerless label paper 3 therebetween. The platen roller 16 is driven rotationally by a drive means not shown, and conveys the linerless label paper 3 to the label paper exit 12 side in conjunction with the printing process.
The label transportation path 13 includes a front transportation guide 21 and a back transportation guide 23. The front transportation guide 21 guides the print side of the linerless label paper 3 from the label paper entrance 11 to the label paper exit 12. The back transportation guide 23 is disposed opposite the front transportation guide 21 and guides the adhesive side of the linerless label paper 3 from the label paper entrance 11 to the label paper exit 12.
The front transportation guide 21 is attached to the case 17 that supports the print head 15, and the back transportation guide 23 and platen roller 16 are attached to the cover 19.
An automatic paper cutter 25 that cuts the linerless label paper 3 discharged from the label paper exit 12 after printing is completed is disposed on the downstream side in front of the label paper exit 12.
The automatic paper cutter 25 cuts the linerless label paper 3 using a cutting blade 26 and a stationary blade 27. The cutting blade 26 can move perpendicularly to the linerless label paper 3, and is disposed to the case 17 on the front transportation guide 21 side. The stationary blade 27 is attached to the cover 19 on the same side as the back transportation guide 23 and platen roller 16.
As shown in FIG. 4, the cover 19 can pivot to the outside on a pin 28 at the bottom of the cover 19, and can thus open the roll paper compartment 7 and the label transportation path 13.
When the cover 19 is open, a label paper roll 5 is set inside the roll paper compartment 7 with a certain length of linerless label paper 3 pulled off the roll, and the cover 19 is then closed, the linerless label paper 3 pulled off the label paper roll 5 inside the roll paper compartment 7 is automatically threaded through the label transportation path 13 and is ready for printing as shown in FIG. 3.
A hollow core 5a on which the linerless label paper 3 is wound is in the center of a conventional label paper roll 5, and the roll paper compartment 7 of the label printer 1 generally supports the label paper roll 5 to rotate freely at a fixed position by means of a support shaft passed through the core 5a. See, for example, Japanese Unexamined Patent Appl. Pub. JP-A-2000-264322.
A problem with this design in which a support shaft through the core 5a of the label paper roll 5 supports the roll to rotate freely is that when the label paper roll 5 is replaced the support shaft must be passed through the core 5a. This makes replacing the label paper roll 5 more time consuming. To shorten the time needed to replace the paper, so-called drop-in loading systems that enable the operator to simply drop the label paper roll 5 into the roll paper compartment 7 without using a support shaft have become more common.
When the label paper roll 5 is used in a drop-in loading system, however, the adhesiveness of the adhesive side of the linerless label paper 3 can cause the entire label paper roll 5 to be pulled toward the label paper entrance 11, resulting in the outside of the label paper roll 5 touching multiple places near the label paper entrance 11. As the outside diameter of the label paper roll 5 changes, the contact points on the outside of the label paper roll 5 also change, the friction produced at each point of contact varies, the load changes when the platen roller 16 advances the label paper, and print defects tend to result from the variation in how much the label paper is advanced. When the diameter of the label paper roll 5 becomes particularly small, the label paper roll 5 can become stuck in the label paper entrance 11 and advancing the paper can be temporarily disabled.
When the linerless label paper 3 is pulled into the label transportation path 13, the linerless label paper 3 is peeled from the outside layer of the label paper roll 5 near the label paper entrance 11. This applies a heavy friction load at the label paper entrance 11, and can easily result in build-up of chaff from label paper wear near the label paper entrance 11. This accumulated chaff is then drawn into the label transportation path 13 where it can readhere to the label transportation path 13 and lead to print defects.